Light Water Reactor fuel integrity is a critical part of overall nuclear reactor safety. The structural integrity of the fuel constitutes a primary barrier to fission product release to the environment, consequently, compromising the structural integrity of the fuel during a fuel cycle is avoided. Compromising the integrity of the fuel (i.e. failure of fuel rods), is avoided by a number of measures taken by the fuel manufacturer or/and operator such as performing refueling outage visual inspections on the fuel rods with underwater equipment, changing the fuel rods, etc. Fuel rods are also tracked as to their respective position and core residence time such that when a fuel rod has a defined amount of depleted fuel, the affected fuel assembly is removed from further reactor operation.
Although best efforts are used to predict fuel rod failure there has been no accurate methodology for prediction of fuel rod failure based upon operating characteristics. Factors such as the extent of use of the fuel rod or the chemistry of reactor water affect the ability of the fuel rod to withstand structural loadings on the rods. Modification of the usage (i.e. using the fuel rod in another position of the reactor) further increases the variability of the fuel rod failure potential. To avoid undesired consequences of fuel rod failure, nuclear plant operators always decide on discharging fuel elements at an earlier time that may present signs of future damage. That decreases economic efficiency for the nuclear power plant.
There is also a need to provide a method to predict fuel rod failure in nuclear fuel assemblies.
There is also a further need to provide a methodology to assess fuel rod integrity during the lifetime of the fuel at a specific point in time, such as during a refueling outage.